Study On Heat Transfer Process And Key Parameters Of Asphalt Functional Layer For Solar Energy Collecting And Snow Melting

Asphalt Pavement Solar System is a new emerging kind of solar energy utilization technology in recent years. It provides an effective solution for high temperature deformation in summer and snow melting in winter of asphalt pavements. Combined with the basic theory of heat transfer and fluid dynamics, the key parameters, which affecting the properties of functional layer of asphalt pavement solar system, have been collaboratively investigated. The decay law of heat collecting and snow melting properties of the functional layer was also studied. The results could provide guidance for the structure design of functional layer and engineering application. The research contents include:(1)The establishment of 3-D unsteady models for heat collecting and snow melting of asphalt pavementBased on Ansys Workbench platform, taking the unsteady flow of heat transfer medium into account, two three-dimensional unsteady models were established: “fluid-pavement-environment” model for heat collecting and “fluid-pavementsnow-environment” model for snow melting. Model verification work was also conducted by indoor heat collecting experiment and outdoor snow melting experiment. The results show that: the accuracy of the two models is satisfying.(2)Collaborative study of the effect of key parameters on heat collecting and snow melting process for the functional layerBased on the established models, it has collaboratively studied the effect of several parameters on heat collecting efficiency and snow melting processes, such as pipe arrangement( diameter, depth, distance), thermal properties of asphalt mixtures and pipe materials(thermal conductivity, specific heat), state of heat transfer medium(inletwater temperature, flow rate). Sensitivity analysis was used to investigate the impact of different parameters on the performance of the functional layer. The results show that: the parameters for heat collecting and snow melting processes are the same, since the two heat transfer processes are inverse. Normally speaking, big diameter, shallow depth, narrow distance can improve the heat transfer for both processes. And pipe diameter and distance are the principal parameters. Besides, improve thermal conductivity of asphalt is also an effective way to improve the heat transfer processes. Flow rate has no significant impact on both heat collecting and snow melting processes. Meanwhile the temperature of heat transfer medium presents huge impact.(3) Decay law study of heat collecting and snow melting propertiesBased on the research results mentioned above, a big scale model with the dimension of 4m×4m was created. And the decay law of heat collecting and snow melting properties were investigated under different climatic conditions.The results show that: although the heat collecting efficiency and temperature rise per unit pipe length decrease along the flow direction, the functional layer can achieve effective temperature reducing for asphalr pavement and heat collecting effect under different summer climatic conditions. And the temperature of outwater depends on ambient air temperature and pipe length. In this study, temperature of outwater can be increased by more than 10℃. The thermal quality of outwater can be greatly improved, which is beneficial for the seasonal energy storage.In the aspect of snow melting in winter, the snow melting effect depends on both temperature of heat transfer medium and ambient air temperature. For a constructed functional layer, the heat flux decreases along the flow direction. And its value mainly depends on the temperature of inletwater. And its drop percent is nearly a constant value, which is inletwater-temperature independent. It can conclude that for a constructed functional layer, the variation of temperature drop per unit length can be calculated according the temperature of inletwater.